Vacuum valves as claimed in the preamble of claim 1 and closure members as claimed in the preamble of claim 11 are known in particular in the form of the transfer valve developed as a rectangular insert valve with the product name “MONOVAT Series 02 and 03” by VAT Vakuumventile AG in Haag, Switzerland. The design and method of operation of such a valve are described in a schematic manner, for example, in U.S. Pat. No. 4,809,950 (Geiser) and U.S. Pat. No. 4,881,717 (Geiser).
In general, vacuum valves for closing in a substantially gas-tight manner a flow path which leads through an opening realized in a valve housing are known in various embodiments from the prior art. Vacuum gate valves are used in particular in the area of integrated circuit and semiconductor production which has to take place in a protected atmosphere, where possible without the presence of contaminated particles. For example, in a manufacturing plant for semiconductor wafers or liquid crystal substrates, the highly sensitive semiconductor or liquid crystal elements sequentially run through several process chambers in which the semiconductor elements, located inside the process chamber, are processed in each case by means of a processing device. Both during the processing process inside the process chamber and during the conveying from process chamber to process chamber, the highly sensitive semiconductor elements must always be situated in a protected atmosphere—in particular in a vacuum. The process chambers are connected together, for example, by passageways, it being possible to open the process chambers by means of vacuum gate valves for transferring the parts from the one process chamber to the next process chamber and to close them subsequently in a gas-tight manner to carry out the respective process stage. These types of valves are also called vacuum transfer valves as a result of the described field of application and also as rectangular gate valves as a result of their rectangular opening cross section.
As transfer valves are used, among other things, during the manufacture of highly-sensitive semiconductor elements, the generation of particles brought about in particular by the actuation of the valve and the number of free particles in the valve chamber have to be kept as low as possible. Particle generation is primarily a consequence of friction, for example as a result of metal-metal contact and as a result of abrasion.
The demands made on the seals that are used with vacuum valves are very high. On the one hand, the tightness of the valve has to be ensured in the closed state of the valve. This is a big challenge above all as a result of the high differential pressures in the vacuum region and the consequently occurring large forces which act on the valve closure. As in the case of excessively large amounts of pressing, the seals used are subject to an above-averagely high level of wear or are destroyed, the design of the valve must be such that the differential pressing forces are not able to act on the seals or can only act on them in a limited manner. In addition, transverse loads and longitudinal loads on the seal are to be kept as small as possible. Above all, in the case of transverse loads transversely with respect to the longitudinal direction of the seal, with O-ring seals there is the risk that they are torn out of their holder, in particular the groove in which they are fixed. Even vulcanized seals may only be exposed to very limited transverse forces. Both in the open and the closed state of the valve, the seals are exposed in part to aggressive media and consequently have to be either created in such a manner that they are able to withstand the influences, and/or that they are moved out of the flow path of the medium, also to avoid abrasion. An excessively high amount of wear on the seal represents an uncertainty factor for process reliability and requires the seal to be regularly replaced, which in turn leads to increased down times in the process.
Various embodiments of vacuum valves, in particular the seal and drive technologies thereof, are known from the prior art and, among other things, the aim thereof is to increase the service life of the seals used as well as to improve process reliability.
Depending on the respective drive technologies, a difference is made in particular between gate valves, also called valve gates or rectangular gates, and shuttle valves, the closing and opening in the prior art being effected in the majority of cases in two stages. In a first stage, a valve closure member, in particular a closure actuator, in the event of a gate valve such as, for example, known from U.S. Pat. No. 6,416,037 (Geiser) or U.S. Pat. No. 6,056,266 (Blecha), in particular of the L-type, is displaced linearly over an opening substantially parallel to the valve seat or in the event of a shuttle valve such as, for example, known from U.S. Pat. No. 6,089,537 (Olmsted), is pivoted about a pivot axis over the opening without at the same time any contact between the closure actuator and the valve seat of the valve housing taking place. In a second stage, the closure actuator is pressed onto the valve seat of the valve housing by way of the closure side thereof such that the opening is closed in a gas-tight manner. The sealing can be effected, for example, either by means of a seal which is arranged on the closure side of the closure actuator and is pressed onto the valve seat which runs around the opening, or by means of a sealing ring on the valve seat, against which the closure side of the closure actuator is pressed. The seal, in particular the sealing ring, can be held and/or vulcanized in a groove.
Various seal devices are known from the prior art, for example from U.S. Pat. No. 6,629,682 B2 (Duelli). A suitable material for sealing rings is, for example, the elastic sealing material known under the trade name of Viton®.
Along with the possibility of controlling the through flow in a precise manner, the advantage above all of the described two-stage movement, where the closure member is first of all pushed transversely over the opening without the seal contacting the valve seat, and the closure member is subsequently pressed substantially vertically onto the valve seat, is that the seal is pressed almost exclusively vertically without the seal being loaded transversely or longitudinally. However, the relatively complex design of the drive, which is formed in particular either by one single drive which enables an L-shaped movement of the closure member, or by a plurality of drives, for example, two linear drives or one linear and one expanding drive, is disadvantageous. Expanding drives, which are arranged in the majority of cases directly behind the closure actuator and adjust said closure actuator in relation to the shaft on which they are situated in the vertical direction onto the valve seat, also have the disadvantage that a multitude of mechanical parts which carry out relative movements with respect to one another are arranged in the valve interior. This increases the complexity of the design, on the one hand, and the generation of friction particles which are harmful to the process, on the other hand. A further disadvantage of the multi-stage movement is the limited adjustment speed of the closure member between the fully open state and the fully closed state. Wedge valves, which are adjusted purely in a linear manner, certainly enable a high adjustment speed, but as a result of the transverse load on the seal are only suitable in a limited manner for use as a main seal in the vacuum region, and if at all, then only for a few adjustment cycles.
Said problem is solved by means of gate valves where the closing and sealing operation is certainly effected by means of one single linear movement, but the seal geometry is in such a manner that a transverse load on the seal is completely avoided. Such a valve is, for example, the transfer valve produced by VAT Vakuumventile AG in Haag, Switzerland which is known under the product name “MONOVAT Series 02 and 03” and is developed as a rectangular insert valve. The design and method of operation of such a valve are described, for example, in U.S. Pat. No. 4,809,950 (Geiser) and U.S. Pat. No. 4,881,717 (Geiser).
The valve described there has in its housing a sealing face which, when viewed in the direction of the axis of the valve passage opening, has portions which are located one behind another and merge by means of constantly extending curvatures into flat sealing face portions which extend laterally outward, the imaginary generatrices of said one-part sealing face which has, however, several portions, lying parallel to the axis of the valve passage opening. The sealing face is machined. The closure member has a supporting face which corresponds thereto for the circumferentially closed seal. Described in more detail, the so-called valve gate has a gate housing and a gate passage opening which is closable by way of a closure member which is displaceable in its plane. In the region of the gate passage opening, there is provided a sealing face against which, in the closed position of the closure member, a circumferentially closed seal, which is arranged thereon, abuts, the imaginary, straight generatrices of the sealing face lying parallel to the axis of the gate passage opening. The circumferentially closed, one-piece seal has portions of various lengths and/or forms which lie in different planes, two main portions of the circumferentially closed seal lying in planes which are at right angles to the axis of the gate passage opening and are spaced apart from one another. The two main portions of the seal are connected by side portions. For the development of the sealing face of the housing, the closure member has a face which extends in a corresponding manner and bears the circumferentially closed seal. The side portions of the circumferentially closed seal extend in a U-shaped manner. In each case, the legs of said side portions which extend in a U-shaped manner lie in a plane. The portions of the sealing face, which are located one behind another when viewed in the axial direction of the gate passage opening, merge into flat sealing face portions which extend laterally outward for the abutment of the main portions of the seal in that region in which they have a common, straight, axially parallel generatrix. Said flat sealing face portions lie in planes which are parallel to one another and to the axis of the gate passage opening.
A suitable drive for such a transfer valve which is closable by means of a linear movement is provided in JP 6241344 (Buriida Fuuberuto). The drive described there has eccentrically mounted levers for linearly displacing the connecting rods on which the closure member is mounted.
US 2008/0053957 A1 (Wakabayashi) describes, among other things, valve gates for substrate processing systems having a kinked or curved valve cross section which are closable either by means of a multiple-stage L-shaped movement or by means of a linear movement.
The valve gate known from the prior art and described in U.S. Pat. No. 4,809,950 (Geiser) is described below by way of FIGS. 8a and 8b. The valve gate shown there in a purely schematic manner has a round opening cross section so as to illustrate better the development of the sealing faces, whilst the transfer valve known under the product name of “MONOVAT Series 02 and 03” and developed as a rectangular insert valve by VAT Vakuumventile AG in Haag, Switzerland has a rectangular opening cross section, the width of which is considerably greater than the height thereof.